Space-borne Bose–Einstein condensation for precision interferometry
Space offers virtually unlimited free-fall in gravity. Bose-Einstein condensation (BEC) enables ineffable low kinetic energies corresponding to pico- or even femtokelvins. The combination of both features makes atom interferometers with unprecedented sensitivity for inertial forces possible and opens a new era for quantum gas experiments. On January 23, 2017, we created Bose-Einstein condensates in space on the sounding rocket mission MAIUS-1 and conducted 110 experiments central to matter-wave interferometry. In particular, we have explored laser cooling and trapping in the presence of large accelerations as experienced during launch, and have studied the evolution, manipulation and interf…
Quantum control theory for decoherence suppression in quantum gates
We show how quantum optimal control theory can help achieve high-fidelity quantum gates in real experimental settings. We discuss several optimization methods (from iterative algorithms to optimization by interference and to impulsive control) and different physical scenarios (from optical lattices to atom chips and to Rydberg atoms).
Theoretical analysis of a realistic atom-chip quantum gate
9 pages, 5 color figures; International audience; We present a detailed, realistic analysis of the implementation of a proposal for a quantum phase gate based on atomic vibrational states, specializing it to neutral rubidium atoms on atom chips. We show how to create a double-well potential with static currents on the atom chips, using for all relevant parameters values that are achieved with present technology. The potential barrier between the two wells can be modified by varying the currents in order to realize a quantum phase gate for qubit states encoded in the atomic external degree of freedom. The gate performance is analyzed through numerical simulations; the operation time is ~10 m…
Mixed internal-external state approach for quantum computation with neutral atoms on atom chips
We present a realistic proposal for the storage and processing of quantum information with cold Rb atoms on atom chips. The qubit states are stored in hyperfine atomic levels with long coherence time, and two-qubit quantum phase gates are realized using the motional states of the atoms. Two-photon Raman transitions are used to transfer the qubit information from the internal to the external degree of freedom. The quantum phase gate is realized in a double-well potential created by slowly varying dc currents in the atom chip wires. Using realistic values for all experimental parameters (currents, magnetic fields, ...) we obtain high gate fidelities (above 99.9%) in short operation times (~ 1…
Collective-Mode Enhanced Matter-Wave Optics
International audience; In contrast to light, matter-wave optics of quantum gases deals with interactions even in free space and for ensembles comprising millions of atoms. We exploit these interactions in a quantum degenerate gas as an adjustable lens for coherent atom optics. By combining an interaction-driven quadrupole-mode excitation of a Bose-Einstein condensate (BEC) with a magnetic lens, we form a time-domain matter-wave lens system. The focus is tuned by the strength of the lensing potential and the oscillatory phase of the quadrupole mode. By placing the focus at infinity, we lower the total internal kinetic energy of a BEC comprising 101(37) thousand atoms in three dimensions to …